Round balers have become quite prevalent for their capability of producing a conveniently sized cylindrical bale, very often automatically wrapped with a sheeting material such as net or film. Crop material, such as hay, is picked up from the ground as the baler travels across the field, and is fed into an expandable chamber where it is rolled up to form a compact cylindrical hay package.
Round balers generally have an expandable bale chamber defined by a pair of fixed sidewalls, and a plurality of side-by-side belts cooperating with a series of transverse rolls, mounted between a pair of pivotally mounted arms commonly known as a sledge. The chamber includes an inlet opening in the front through which crop material is fed. Also included is a pair of take up arms pivotally mounted on the main frame, between which arms multiple guide rolls are journalled. A biasing force is applied on the take up arms to urge the outer surfaces of the guide rolls against the belts to maintain belt tension and prevent slack from occurring in the belts during expansion and contraction of the chamber.
Because it is not uncommon for windrows of crop material to be narrower than the width of the bale forming chamber, additional steps are necessary to uniformly distribute the hay transversely to avoid poorly shaped bales. Operators were once tasked to watch the growing bale, judge its uniformity, and steer the baler along a path that would more uniformly transversely distribute the crop in the bale chamber. More modern round balers often include sub-systems to monitor and control movement of the belts to produce bales of a desired size, shape uniformity, or density. Bale size monitoring is commonly accomplished through the potentiometers connected by linkages to measuring springs disposed on the side walls of the bale chamber. As the bale grows in the chamber, contact with and deflection of the transversely disposed measuring springs provides an indication of the transverse uniformity of the forming bale.
Measuring springs are easily deformed or broken by turbulent crop flow in the bale forming chamber. Turbulent crop flow results in crop moving in a direction reversed from the normal direction of movement, particularly adjacent to the side walls where the measuring springs are located. As the springs typically have a free end projecting into the bale forming chamber, crop moving in the reverse direction wedges between the free end of the measuring spring and the side wall, causing the measuring spring to be bent or broken. Further, the spring ends tend to be honed to a dangerously sharp edge by friction of the passing crop.
It would be desirable to provide a sensing mechanism that would provide a reliable indication of transverse bale size as a bale forms in a bale-forming chamber that withstands turbulent crop flow in the chamber without adverse impact on the bale measuring function. Additional advantages would be realized by a sensing mechanism in a bale chamber that is shaped to prevent gaps in which turbulent crop flow can accumulate thereby reducing the likelihood of damage or mal-adjustment of a bale measuring apparatus. Still further advantages would be realized by a bale size sensing mechanism that is formed of robust materials offering improve durability while providing a reliable and easily calibrated base shape monitoring sensing mechanism.